gnome-app-install does not support multiple packages provding the same
application (e.g. totem-xine, totem-gstreamer). I think we should support a
simple notation of or-style dependencies for g-a-i. The semantic should be
(example: (totem-gstreamer | totem-xine)
1. For new installs:
- pick the first in the | line (e.g. totem-gstreamer)
2. For removals:
- remove all in the | line (e.g. totem-gstreamer and totem-xine
3. For install checks:
- check if one or the other is installed

(In reply to comment #3)
This sounds good, but we'd have to maintain diffs for each menu entry we change,
since regenerating them from a repository will put the old packages back. This
could present a problem sometime in the future, since pyxdg doesn't maintain the
line order in .desktop files, but diff might be able to handle that (?). The
actual support probably easy to do with a Debian package, but I don't really
know how. I'll go ahead and add support for that syntax, and while I'm at it,
I'll probably take care of ANDs (i.e. "abiword & abiword-plugins" as well.

I doubt any of this is still relevant, but I thought I should point out that although the branches Michael pointed out don't exist on my server anymore, they're still on the supermirror: http://<email address hidden>/